Combined telephone-receiver and microphone.



No. 882,135. PAT'ENTED 001. 2, 1906. 0. E. LJUNGMAN, 'R. 0. P. BERGLUND & W. A. W. E. HJORTH.

COMBINED TELEPHONE RECEIVER AND MICROPHONE.

APPLIUATION FILED IEB.14. 1906. I

' INVENTO/ig THE NORRIS PETERS Cm, WASHINGTON, 0. c.

UNITED STATES PATENT OFFICE.

CARL ERNST LJUNGMAN, ROBERT OTTO PERCIVAL BERGLUND, AND WVALTER AXEL WILHELM EMANUEL HJORTH, OF STOCKHOLM,

SWVEDEN.

Specification of Letters Patent.

Patented Oct. 2, 1906.

Application filed February 14:, 1906. Serial No. 301,025.

T0 on whom it may concern:

Be it known that we, CARL ERNST LIUNG- MAN, ROBERT OTTO PEROIVAL BERGLUND, and WALTER AXEL WILHELM EMANUEL HJORTH, subjects of the King of Sweden, residing at 8 lVIiister-Samuelsgatau, Stockholm, Sweden, have invented new and useful In1- provements in a Combined Telephone-Receiver and Microphone, of which the following is a specification.

In telephone apparatus where the micro-- phone and the receiver are both inclosed within the same casing, it has been proposed to prevent sounding and singing of the receiver by locating the mi crophone-diaphragm in an inclined position in relation to the diaphragm of the receiver, the oscillations of the receiverdiaphragm as a result not being transmitted perpendicularly to the microphone-diaphragm, and consequently not, or but little, influencing the latter. It has been found, however, that the desired result cannot always be obtained by making the microphonediaphragm inclined in this manner, and this has led to the invention of another device, which has proved capable under all conditions to prevent the sounding or singing of the receiver. This device, which in the accompanying drawing is shown in section as applied to a microtelephone, consists in arranging between the microphone-diaphragm a and the receiver-diaphragm b a curved screen or disk f, of either conducting or nonconducting material and preferably of parabolical shape, though it may have any other curvature. This disk introduced between the diaphragm has proved to prevent entirely the transmission of the oscillations of the receiver-diaphragm to the microphonediaphragm. For this purpose, however, the screen or disk, as proved by experiment, has to be curved and must not be plane. It has, moreover, been found advantageous to place the curved disk in such a manner that its concave surface will face the receiv er-diaphragm; Good results, however, have also been attained with the disk in the reverse position.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is 1. In a telephone apparatus with receiver .-and microphone Within the same casing, a

curved screen or disk f arranged between the diaphragms of the microphone and of the receiver.

2. In a telephone apparatus with receiver and microphone within the same casing, a

screen or disk f arranged between the diaphragms of the microphone and the receiver said screen or disk being symmetrically curved from the center.

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

CARL ERNST LJUNGMAN. ROBERT OTTO PERCIVAL BERGLUND. WALTER AXEL WILHELM EMANUEL HJORTH.

Witnesses:

J. A. MARKMAN, H. FELANDER. 

